There has been known in the prior art such a suspension system that front and rear wheels are mounted on a vehicle body through suspension cylinders in order to prevent the passage, up to the vehicle body, of the bouncing of the front and rear wheels during a drive along a rough road.
The vehicle body provided with this type of suspension system undesirably tends to make an outward tilt, or a body roll, on cornering, with a centrifugal force acting to contract the outer suspension cylinders of the motor vehicle.
In order to prevent the body roll, therefore, there has been adopted a means to detect a steering angle or a steering angular velocity when the steering wheel is manipulated, for the purpose of increasing a damping force of the outer suspension cylinders of the vehicle when the vehicle is rounding a curve, thereby restraining suspensions' contraction caused by the centrifugal force.
However, in the detection of the steering angle alone, the steering wheel must be turned to a set steering angle to obtain a desired damping force of the suspension cylinders. That is, the suspension cylinders can not quickly respond to steering conditions, and therefore a vehicle body roll in the initial period of a turn can not be prevented.
In the detection of the steering angular velocity, when the vehicle is turned on a fixed circle with the steering wheel fixed at a prescribed steering angle, the damping force of the outer suspension cylinders can not be increased and accordingly it is impossible to prevent a body roll.